In recent years, printed wiring boards configured highly densely by a multi-layer structure have been used. A connector for high-speed transmission is mounted on an end of a printed wiring board. Thus, by mounting the connector for high-speed transmission on the printed wiring board, high-speed transmission is enabled between the printed wiring board and another board via the connector.
Hereinafter, an overview of the configuration of a connector will be described with reference to FIGS. 11 to 13. FIG. 11 is a perspective view illustrating the outer appearance of a printed wiring board. FIG. 12 is a plan view illustrating a connector in FIG. 11. FIG. 13 is a sectional view taken along the line A-A of FIG. 12.
As illustrated in FIGS. 11 to 13, a connector 10 is mounted on the end of a printed wiring board 1 and is configured by joining and combining a plurality of connector plates 11 (six connector plates in FIGS. 11 and 12) with a blade shape. When the plurality of connector plates 11 is joined to each other, the joined connector plates 11 are integrally fixed by fixing plates 25.
The connector plate 11 is formed of a resin plate that has an entire thin plate shape and a substantial L shape and includes an upper-side plate 12 and a lateral-side plate 13. A connector pin 20 that is electrically connected to a signal line 4 embedded in a board body 2 of the printed wiring board 1 is installed inside the connector plate 11.
The connector pin 20 includes a plurality of a pin members 21 (three pin members in FIG. 13). The pin member 21 includes connection pins 22 that extend in a predetermined direction (the lower side in FIGS. 11 and 13) and pin terminals 23 that are disposed in concave portions 14 of the lateral-side plate 13. The connection pins 22 of the connector pin 20 serve as input/output terminals of an electric signal transmitted from the signal line 4 of the printed wiring board 1. The pin terminals 23 of the connector pin 20 serve input/output terminals that input and output an electric signal transmitted from the connection pins 22 to connector pins of another connector (not illustrated).
As illustrated in FIG. 13, the connector 10 is press-fitted and fixed to a predetermined position (an end in FIG. 13) of the printed wiring board 1. That is, an electric signal transmitted from the signal line 4 of the printed wiring board 1 is transmitted to another connector via the connection pins 22 and the pin terminals 23 of the connector pin 20 of the connector 10. An electric signal from another connector is transmitted to the signal line 4 of the printed wiring board 1 via the connection pins 22 and the pin terminals 23 of the connector pin 20 of the connector 10.    Patent Document 1: Japanese Laid-open Patent Publication No. 2003-283093    Patent Document 2: Japanese Laid-open Patent Publication No. 11-251539
However, the connector plates 11 included in the connector 10 use a method of press-fitting and fixing the connector pins 20 from one side (the front surface L side in FIGS. 11, 12, and 13) to the printed wiring board 1. Therefore, there is a problem that an electric signal transmitted from the signal line 4 of the printed wiring board 1 or an electric signal transmitted through another connector may be attenuated due to the influence of a stub to be described below, and thus transmission quality or transmission efficiency of the electric signal may deteriorate.
That is, as illustrated in FIG. 13, the signal line 4 provided in the printed wiring board 1 is embedded in the board body 2 in the horizontal direction (traverse direction in FIG. 13). Further, through holes 3 formed in the printed wiring board 1 are through holes that penetrate the board body 2 in the vertical direction (the longitudinal direction in FIG. 13).
Therefore, when the connector 10 is press-fitted and fixed to the printed wiring board 1, the through holes 3 of the printed wiring board 1 are connected to the connection pins 22 of the connector pins 20 of the connector plates 11, and thus signal transmission paths between the signal line 4 and the connector 10 are formed. In this case, however, the transmission paths of an electric signal transmitted from the signal line 4 or an electric signal transmitted from another connector are branched in two directions.
Specifically, one transmission path (transmission path branched to the lower side in FIG. 13) of the transmission paths branched in two directions becomes a stub. As illustrated in FIG. 13, when the signal line 4 of the printed wiring board 1 is embedded at a position close to the front surface L side of the board body 2, the length of the stub is longer than the length of the transmission path directly transmitted from the signal line 4 via the connection pin 22.
That is, due the influence of the stub, the electric signal transmitted from the signal line 4 by the stub or the electric signal transmitted from another connector is reflected at the front end of the stub via the transmission path by the stub. Then, an attenuation phenomenon in which the electric signal is attenuated occurs due to the resonance of the signal reflected in this way. Thus, the deterioration in the transmission quality or transmission efficiency of the electric signal of the signal line 4 may cause deterioration in high-speed of signal transmission.
Further, when the transmission path of the stub side is long and the transmission speed is high, the electric signal is easily attenuated. That is, there is a problem that the attenuation phenomenon of the electric signal caused due to the stub may easily occur in a high-speed transmission path.
In recent years, as an LSI (Large Scale Integration) has a high function, the number of signal lines 4 embedded in the printed wiring board 1 increases and the plate thickness of the board is thickened, and thus the length of the stub side is lengthened. For this reason, a connector suppressing an adverse influence caused due to the stub is preferably realized.
Accordingly, to resolve the adverse influence caused due to the stub, a back drill process of scraping off a part of the stub is performed through counter-boring by a back drill. However, when the back drill process is performed, there are problems that a working process may become complicated, a yield ratio may be reduced due to an extra work, and a manufacturing cost of the printed wiring board may increase.